feat: support the /v1/video/generation for wan2.2.

[ethan686]

No description provided.

[gemini-code-assist]

Code Review

This pull request introduces video generation support across the xLLM stack, including new RPC endpoints, service implementations, and an FFmpeg-based in-memory video encoder. The core DiT framework was updated to handle video-specific parameters and tensors like last_images and image_embeds. Review feedback highlights a critical bug in frame count logic for 3D tensors and missing serialization logic in the shared memory manager. Additionally, several style guide violations were identified concerning fixed-width integer usage, the 'final' keyword for classes, and inappropriate use of 'auto' for simple types. A typo in the protobuf field 'guidence_scale_2' also needs correction.